ABSTRACT
This chapter discusses two algorithms as examples: particle tracing and path tracing. The first is useful for walkthrough applications such as maze games, and as a component of batch rendering. The second is useful for realistic batch rendering. The chapter also discusses separating out "direct" lighting where light takes exactly once bounce between luminaire and camera. Many surfaces in the real world receive most or all of their incident light from other reflective surfaces. This is often called indirect lighting or mutual illumination. The chapter presents a more physically based method of direct lighting. These methods will be useful in making global illumination algorithms more efficient. The global illumination algorithms can be adjusted to make sure they compute the direct component exactly once. For example, in particle tracing, particles coming directly from the luminaire would not be logged, so the particles would only encode indirect lighting.
